Can't download bt notifications on iPhone 5s, what can I do?

I recently bought the U8 Uwatch pro smart watch and I have it connected to an iPhone 5s but not everything works. To get everything working I need to install the bt notifications so I download a file from the website the watch says to an app that I needed to install to have access to that file, but then I can't download it onto my phone which is what I need to do. What can I do to get the bt notifications downloaded onto my phone and fully working?

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